Structured abrasive articles are a specific type of coated abrasive article that has a plurality of shaped abrasive composites secured to a major surface of a backing. Each shaped abrasive composite has a bottom surface in contact with the backing and a distal end that extends outwardly from the backing. The shaped abrasive composites comprise abrasive particles dispersed in a binder matrix, typically including a crosslinked organic polymer. The shaped abrasive composites are usually arranged in an array. In one common configuration of a structured abrasive article, the shaped abrasive composites are pyramidal (e.g., tetrahedral or square pyramidal).
Traditionally, structured abrasive products such as, for example, those available as TRIZACT STRUCTURED ABRASIVE from 3M Company of St. Paul, Minn., have utilized pyramidal abrasive composites. Pyramids are typically used for a variety of reasons, not all of them based on abrading performance. For example, pyramids are an easy shape to produce in the tooling used in the manufacture of the structured abrasive products. Further, during manufacture, the tooling is typically relatively easy to fill with curable slurry and separate from the structured abrasive article after curing when pyramids are used.
A characteristic of pyramidal abrasive composites is a change in load-bearing area from the tops of the shaped composites to their bottom surfaces as they erode during use. Initially, the erosion is rather rapid. With continued use the load-bearing area increases until it reaches a point beyond which it no longer breaks down and stops efficiently abrading. This usually occurs when the load-bearing area is in a range of from fifty to seventy percent of the area of the working abrasive surface. In practice, this has limited the useful life of structured abrasive articles incorporating pyramidal shaped features.
Use of alternate designs for the shaped abrasive composites to overcome this problem is described in U.S. Pat. No. 8,425,278 B2 (Culler et al.). In that approach, cusps were formed at intersections of sidewalls and a grinding surface that included a recessed feature. However, in practice, problems with filling the mold cavities in the production tool may lead to malformed cusps, thereby reducing the reliability of the abrading performance of the resulting structured abrasive article or manufacturing yield.
Accordingly, there remains a need for structured abrasive articles that provide superior abrading properties to structured abrasive articles with pyramidal abrasive composites, while overcoming fill problems associated with the shaped abrasive composites described in U.S. Pat. No. 8,425,278 B2 (Culler et al.).